Endocardial Fibroelastosis

Synonyms of Endocardial Fibroelastosis

EFE

Elastic tissue hyperplasia

Endocardial Dysplasia

Endocardial sclerosis

Fetal Endomyocardial Fibrosis

Subendocardial Sclerosis

General Discussion

Endocardial fibroelastosis (EFE) is a rare heart disorder that affects infants and children. It is characterized by a thickening within the muscular lining of the heart chambers due to an increase in the amount of supporting connective tissue (inelastic collagen) and elastic fibers. The normal heart has four chambers. Two chambers, known as atria, are separated from each other by a partition called the atrial septum. The other two chambers, known as ventricles, are also separated by a septum. Valves connect the atria (left and right) to their respective ventricles.

The symptoms of endocardial fibroelastosis are related to the overgrowth of fibrous tissues causing abnormal enlargement of the heart (cardiac hypertrophy), especially the left ventricle. Impaired heart and lung function eventually lead to congestive heart failure. Endocardial fibroelastosis may occur for no apparent reason (sporadic) or may be inherited as an X-linked (EFE2) or autosomal recessive (EFE1) genetic trait.

Signs & Symptoms

The symptoms of endocardial fibroelastosis begin rapidly, generally between the ages of 4 and 12 months. Symptoms are due to the overgrowth of fibrous tissue and thickening of the lining of the hearts’ chambers (i.e., endocardium and subendocardium), especially the left ventricle. In some very rare cases of EFE, the left ventricle is small (hypoplastic) or of normal size and the right ventricle is enlarged.

The most common symptoms of endocardial fibroelastosis include difficulty breathing (dyspnea), breathlessness, grunting sounds during breathing, coughing, irritability, weakness, and/or a pale facial appearance (pallor). Other symptoms may include fatigue, failure to thrive, increased sweating, an abnormal blue skin coloration on the feet and hands (peripheral cyanosis), and/or wheezing.

Infants and children with endocardial fibroelastosis may have unusual chest sounds that can be heard during a physician’s examination with a stethoscope. Bubbling, moist sounds (rales) suggest fluid accumulation in the airways. Unusual heart sounds (murmurs) are also typically present in children with EFE. Excessive backward flow of blood from the left ventricle, through the mitral valve and into the left atrium (mitral regurgitation) is also a common finding in children with this disorder. Symptoms of mitral regurgitation may include heart palpitation and intolerance to exercise.

Causes

Some cases of endocardial fibroelastosis occur as a result of random changes (mutations), with no apparent cause (sporadic). These cases are known as endocardial fibroelastosis 1 (EFE1). Others cases are thought to be inherited as an X-linked recessive genetic trait. These cases are known as endocardial fibroelastosis 2 (EFE2). In EFE1, neither the chromosome nor the precise location of the mutated gene on that chromosome have been determined. In EFE2, the mutated gene is located on the X chromosome, but its precise location is not known.

Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 11p13” refers to band 13 on the short arm of chromosome 11. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.

Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one of the X chromosomes is “turned off” and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is “turned off”. A male has one X chromosome and if he inherits an X chromosome that contains a disease gene, he will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.

X-linked dominant disorders are also caused by an abnormal gene on the X chromosome, but in these rare conditions, females with an abnormal gene are affected with the disease. Males with an abnormal gene are more severely affected than females, and many of these males do not survive.

Other cases of endocardial fibroelastosis are thought to occur in association with other metabolic defects, such as Barth syndrome or carnitine deficiency syndromes. (See Related Disorders section of this report.)

Affected Populations

Endocardial fibroelastosis is a rare disorder that affects males and females in equal numbers. Fewer than 1 percent of infants and children with congenital heart disease are diagnosed with this disorder. A 1964 study suggested an incidence of 1 in 5,000 live births. However, in the United States there has been a marked reduction in incidence since then for reasons that are not known. The disorder is extremely rare.

Related Disorders

Symptoms of the following disorders can be similar to those of Endocardial Fibroelastosis. Comparisons may be useful for a differential diagnosis:

Barth Syndrome, also known as Cardioskeletal Myopathy with Neutropenia and Abnormal Mitochondria, is a rare inherited metabolic disorder. Symptoms may include low levels of certain white blood cells (agranulocytopenia), muscle weakness, and/or abnormal enlargement of the heart (hypertrophic cardiomyopathy) leading to congestive heart failure. Failure to thrive, growth delays, and/or recurring respiratory infections are common in children with Barth Syndrome. Some affected infants also have Endocardial Fibroelastosis. Barth Syndrome is inherited as an X-linked genetic trait.

Carnitine Deficiency Syndrome is a rare metabolic disorder that may be inherited in some cases, or occur as a result of other metabolic disorders. Carnitine functions in the body as a carrier of fatty acids to the energy centers in muscles (mitochondria). Muscle weakness is the primary symptom of Myopathic Carnitine Deficiency Syndrome. The symptoms of Systemic Carnitine Deficiency Syndrome may include the gradual degeneration of the brain (encephalopathy), episodes of vomiting, confusion, and/or stupor that progresses to coma. Carnitine Deficiency Syndrome may also be associated with low blood sugar (hypoglycemia). Damage to the heart may result in chronic disease (cardiomyopathy). (For more information on this disorder, choose “Carnitine Deficiency” as your search term in the Rarte Disease Database.)

Hypoplastic Left Heart Syndrome is a term used to describe a group of closely related rare heart defects that are present at birth (congenital). This disorder is characterized by the underdevelopment (hypoplasia) of the chambers on the left side of the heart (i.e., left atrium and ventricle). In addition, the mitral valve, which connects these chambers to each other, is usually abnormally narrow (stenosis) or closed (atresia). Symptoms of Hypoplastic Left Heart Syndrome may include difficulty breathing (dyspnea), a high-pitched noise while inhaling (rales), a grayish-blue color of the skin during the first 48 hours of life, and/or an abnormally enlarged liver (hepatomegaly) . Other symptoms may include poor feeding habits, frequent vomiting, lethargy, and/or shock. (For more information on this disorder, choose “Hypoplastic Left Heart” as your search term in the Rare Disease Database.)

Atrioventricular Septal Defect is a rare heart defect that is present at birth (congenital) and is characterized by the improper development of the septa and valves (atrial and ventricular septa and atrioventricular valves). Infants with the complete form of Atrioventricular Septal Defect usually develop congestive heart failure. Excessive fluid also accumulates around the heart and lungs, and this congestion may lead to difficulty breathing (dyspnea). Other symptoms may include a bluish discoloration of the skin and mucous membranes (cyanosis), poor feeding, abnormally rapid breathing (tachypnea), excessive sweating, and/or an abnormally rapid heartbeat (tachycardia). (For more information on this disorder, choose “Atrioventricular Septal Defect” as your search term in the Rare Disease Database.)

Atrial Septal Defects are congenital heart defects characterized by the presence of a small opening between the two atria of the heart. This defect leads to an increase in the work load on the right side of heart, and excessive blood flow to the lungs. The symptoms, which may become apparent during infancy, childhood, or adulthood, can vary greatly and depend on the severity of the defect. The symptoms tend to be mild at first and may include difficulty breathing (dyspnea), increased susceptibility to respiratory infections, and/or an abnormal bluish discoloration of the skin and mucous membranes (cyanosis). Some people with Atrial Septal Defects may be at increased risk for the formation of blood clots that can travel to the major arteries (embolism), possibly blocking blood circulation. (For more information on this disorder, choose “Atrial Septal Defects” as your search term in the Rare Disease Database.)

Ventricular Septal Defects (Cor Triloculare Biventricularis) are a group of congenital heart defects characterized by the absence of one atrium. Infants with this defect have 2 ventricles and 1 large atrium. Symptoms of these defects may include an abnormally rapid rate of breathing (tachypnea), wheezing, a rapid heartbeat (tachycardia), and/or an abnormally enlarged liver (hepatomegaly). Ventricular Septal Defects can also cause the excessive accumulation of fluid around the heart, leading to congestive heart failure. (For more information on this disorder, choose “Ventricular Septal Defects” as your search term in the Rare Disease Database.)

Cor Triatriatum is an extremely rare congenital heart defect characterized by the presence of an extra chamber above the left atrium of the heart. The pulmonary veins, returning blood from the lungs, drain into this extra “third atrium.” The symptoms of Cor Triatriatum vary greatly and depend on the size of the opening between the chambers. Symptoms may include abnormally rapid breathing (tachypnea), wheezing, coughing, and/or abnormal accumulation of fluid in the lungs (pulmonary edema). (For more information on this disorder, choose “Cor Triatriatum” as your search term in the Rare Disease Database.)

Cor Triloculare Biatriatum is an extremely rare congenital heart defect characterized by the absence of one ventricle. Infants with this defect have two atria and one large ventricle. The symptoms may include breathing difficulties (dyspnea), excessive accumulation of fluid in the lungs (pulmonary edema) and around the heart, and/or a bluish discoloration of the skin and mucous membranes (cyanosis). Other symptoms may include poor feeding habits, abnormally rapid breathing (tachypnea), and/or an abnormally rapid heartbeat (tachycardia).

Cardiomyopathies are a group of diseases that affect the muscular tissue of the heart and may occur for no known reason (Idiopathic Cardiomyopathy). These disorders are usually characterized by abnormal enlargement of the heart leading to impairment in cardiac function. Symptoms may include difficulty breathing, an abnormal bluish discoloration of the skin (cyanosis), abnormally rapid heart beat (tachycardia), and/or congestive heart failure. Cardiomyopathies may occur at any age.

Infective Myocarditis may be caused by a virus and is characterized by difficulty breathing (dyspnea), abnormal enlargement of the heart, an unusually rapid heartbeat (tachycardia), irregular heart rhythms (arrhythmias), and/or fluid accumulation and swelling, especially in the arms, legs, and face (edema).

Diagnosis

The diagnosis of endocardial fibroelastosis is confirmed by a thorough clinical evaluation, including a physical examination that may reveal signs of respiratory distress (i.e., moist rales) and galloping heart rhythms. Radiographic studies (x-ray) of the chest typically reveal abnormal enlargement of the heart, especially the left ventricle (ventricular hypertrophy). Damage to the heart may be demonstrated by measuring the electrical activity of the heart (i.e., electrocardiogram [EKG]). This test may show subtle changes (i.e., S-T segment and T-wave changes) that strongly suggest damage to the heart that is characteristic of EFE. Repeated electrocardiograms may be required to monitor changes in heart function.

Standard Therapies

Treatment

Infants who are diagnosed early in the course of the disease respond more favorably to treatment than those who are not diagnosed until substantial heart damage has already occurred. Treatment for EFE is essentially the same as for chronic heart failure. A variety of drugs may be used to help control congestive heart failure that is associated with EFE, and to reduce heart rate and improve the ability of the heart to contract. Diuretics may be used to eliminate fluids from the body. Drugs that help maintain normal heart rhythm (i.e., antiarrhythmics) may be administered to correct arrhythmias. Medications that prevent the clotting of blood (anticoagulants) may also be necessary. Prolonged bed rest may facilitate healing of myocardial lesions since the heart is working at a reduced load when a person rests.

For some children with advanced illness, heart transplantation may be the treatment of last resort.

Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:

Years Published

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